OBJECTIVE: To determine, in a group of eutrophic children and adolescents, the values of fasting leptinemia and its correlation with age and body mass index. METHODS: A cross-sectional study conducted in two public schoolsin Ribeirao Preto, Brazil. Anthropometric measurements and venous blood samples were obtained for determination of fasting leptinemia of 448 eutrophic and medium maturers children and adolescents, of both genders, aged between 7 and 17.9 years. Using the Mann-Whitney test, comparisons were made between the concentrations obtained for boys and girls in each age group. Subsequently, using the Kruskal-Wallis test, values were compared in each age group and, using the Spearman correlation test, the correlations between fasting leptinemia and age and between fasting leptinemia and the z-scores of body mass index were assessed. RESULTS: Fastingleptinemia values differed between boys and girls in all age groups and it was higher for girls. Among boys, the values of leptinemia did not show statistically significant variation; among girls, there was variability, with gradual increase according to age group. The correlation study showed positive correlation between leptinemia and z-scores of body mass index in both genders and between leptinemia and age only for girls. CONCLUSION: The data show the necessity of establishing reference curves for fasting leptinemia taking into account gender age and body mass index.